This invention relates to improved methods and apparatus for completing, producing and servicing wells, and in particular to improved methods and apparatus for separately isolating and treating multiple hydrocarbon bearing subterranean zones in a well. The methods and apparatus of the present invention are applicable to isolating well zones for treatment production, testing, completion and the like.
It is common to encounter hydrocarbons wells intersecting more than one separate subterranean hydrocarbons bearing zones. These separate zones can have the same or different characteristics. Production of hydrocarbons from subterranean zones can be enhanced by performing various treatments to the zones. Examples of well treatments include fracturing, perforating, gravel packing, chemical treatment, and the like. The zone""s particular characteristics determine the ideal treatments to be used. In multi zone wells, different well treatments may be required to properly treat the zones.
For example, the production of hydrocarbons from unconsolidated or poorly consolidated formation zones may result in the production of sand along with the hydrocarbons. The presence of formation fines and sand is disadvantageous and undesirable in that the particles abrade pumping and other producing equipment and reduce the fluid production capabilities of the producing zones in the wells. Particulate material (e.g., sand) may be present due to the nature of a subterranean formation and/or because of well stimulation treatments wherein proppant is introduced into a subterranean formation. Unconsolidated subterranean zones may be stimulated by creating fractures in the zones and depositing particulate proppant material in the fractures to maintain them in open positions.
Gravel pack treatments with and without sand screens and the like have commonly been installed in wellbores penetrating unconsolidated zones to control sand production from a well. The gravel pack treatments serve as filters and help to assure that fines and sand do not migrate with produced fluids into the wellbore.
In a typical gravel pack completion, a screen consisting of screen units is placed in the wellbore within the zone to be completed. The screen is typically connected to a tool having a packer and a crossover. The tool is in turn connected to a work or production string. A particulate material, usually graded sand (often referred to in the art as gravel) is pumped in a slurry down the work or production string and through the crossover whereby it flows into the annulus between the screen and the wellbore. The liquid forming the slurry leaks off into the subterranean zone and/or through a screen sized to prevent the sand in the slurry from flowing there through. As a result, the sand is deposited in the annulus around the screen whereby it forms a gravel pack. The size of the sand in the gravel pack is selected such that it prevents formation fines and sand from flowing into the wellbore with produced fluids.
Circulation packing (sometimes called xe2x80x9cconventionalxe2x80x9d gravel-packing) begins at the bottom of the screen and packs upward along the length of the screen. Gravel is transported into the annulus between the screen and casing (or the screen and the open hole) where it is packed into position from the bottom of the completion interval upward. The transport fluid then returns to the annulus through the washpipe inside the screen that is connected to the workstring.
After gravel packing it is sometimes necessary to perform additional and different treatments on the gravel packed zone after its production performance has been monitored and evaluated.
As pointed out above, when a well intersects multiple spaced formation zones, each zone may require separate or even different successive treatments. In these multiple zone wells, a need arises to mechanically isolate the separate zones so that they may be individually treated. In the selected gravel packing treatment example, a multiple zone well may require that each zone be isolated and connected to the surface and treated individually. For example, undesirable fluid losses and control problems could prevent simultaneous gravel packing of multiple zones. In addition, each zone may require unique treatment procedures and subsequent individual zone testing and treatment may be required.
Conventional methods of isolating individual zones for treatment, utilize multi-trip processes of setting temporary packers. The packers are first set, the isolated zone treated and the packers removed. To overcome these time consuming and expensive conventional methods one-time hydraulic operated sleeves have been used to provide access to a zone after it has first been treated. When the zone is to be opened the tools"" hydraulically operated sleeve valve is opened as the well pressure is raised to a preset level and then bled off. These tools are one-shot in that they are installed in the closed position and once opened cannot be later closed to again isolate that particular zone. These prior systems and methods do not allow the zones to be selectively and repeatedly isolated for subsequent treatment and monitoring.
Thus, there are needs for improved methods and apparatus for completing wells, including providing a simple, cost-effective method and apparatus for individually and repeatedly isolating and treating multiple zones in a single well.
The present invention provides improved methods and apparatus for isolating multiple hydrocarbon bearing zones in wells, including selectively and repeated isolation of individual zones in a well. More specifically, the present invention provides a zone isolation apparatus, which can be repeatedly opened and closed. This allows well zones to be selectively and individually treated or tested as may be required. This apparatus and method eliminates the costly and time consuming process of setting and removing packers each time the zone must be isolated.
The improved methods and apparatus basically comprise the steps of placing upper zone isolation apparatus on one or more of the zones of a well. In gravel packing the isolation apparatus is run in the well with the gravel pack-packer and screens and later opened and closed as required.
The improved methods and apparatus of the present invention, in one embodiment, utilizes a valve selectively providing fluid communication with a well zone isolated in an annulus between packers. The valve can be opened and closed by engaging and moving a sleeve accessible from the well surface through the well tubing. The valve is also remotely hydraulically actuateable by manipulating the downhole pressures.
Other and further objects, features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of preferred embodiments which follows when taken in conjunction with the accompanying drawings, in which: